Process for the recov ery of zinc oxide from zinciferous materials



C. W. TIIYIIII PROCESS FDH THE RECOVERY UF ZINC OXIDE FHOIII ZINCII'EHOUS I'IIAIERIMS, ESPECIALLYSIMSJ AI PlICAIOII FILED AIII. fl II 19| 3- ff fr f/ Vratus and filter sprays.

UNITED STATES. PATENT OFFICE.

FRIEDRlCI-I CARL WILHELM TIMM. OF HAMBURG. GERMANY.

Pnociss Fon THE RECOVERY or ZINC oxIDE FROM zINcrFERoUs Marleen/ils,

' ESPECIALLY sLAGs.

Application illed April 29, 1913,

Specification of Letters Batent.

Patented Mar. 14, i922.

Serial No. 764,349.

(GRANTED UNDER THE IROVISIONS 0F THE ACT 0F MARCH 3. 1921. 41 STAT. L., 1313.)

To (1l-Z whom it om); concern:

Be it known that l. Flusnlucn (Hun, Vilmiismi Tiuil. a subject of the Emperor of Germany. residing at Hamburg. Germany` have invented new and useful Improvements in Processes for the Recovery ot' Zinc Oxide from Zinci'ferous Materials. Especially Ships1 of which the followingv is a specification.

This invention relates to a process for the separation ot' zinc from zinciferous mate-Y rials which are either easily melted hy themselves, as for example the slags from lead and copper furnaces., or may he obtained in a molten Condition h v the addition of suitable tiuxes. The separated zinc is recovered in the form ot' zinc oxide. The zinc may be contained in the materials in the form of oxide, silicate` sulphide or other conihination.

In the accompanying drawing Figures l and Q illustrate in vertical section two furnaces suitable tor working the process. similar letters ot reference relating to like parts therein.

In Figure 1 O is a blast furnace to which the Charce is introduced through the opening (ir. rThe opening (l is covered by a plate. H which is taken oil" on introducing the charge. 0n a grateof watercooled pipes C rests the dezincifving layer B and on this the charge .l whic i contains the materials to be dezincified. At the side of the furnace O is provided a furnace grate J the hot gases of combustion from which enter thc furnace at the top and pass downwards through the grate` whereupon they escape through the conduit F` and pass into the cooling appa- Through the grate also flows the molten and dezinciiied residue which passes out of the. furnace through the, openings l) and is introduced into slag moulds hy means of a spout E iu the familiar manner.

lf it is desired to tire with gas instead of with a furnace grate` gas is admitted through the opening l( and is hurned hy means of air which entersl through the pipe l1.

The furnace shown in Figure 2 is quite similarly constituted. hut in it, the heat necessary is produced in the charge itself hy the combustion of coke or coal. For this purpose the air for combustion enters the charge from the main air cliannel M through thevnozzlcs X. 'l`hc coke burns in front; ot the nozzles and thc damper R in the educ- 5.5`

'tion pipe Q is so adjusted that part of the gases escapes upwards through Q, and the other part escapes downwards through con-- duit l". ln this case the dezii'icifying layer does not rest on a grate but directly on the floor of the furnace so that the gases and the llezincitied molten residue pass out through the opening l. The molten residue then passes on through the opening D to the spout E.

The process inter alia aims at making materials available. which on account ot their eas) tusibility and of their small zinc. content, do not allow of treatment with economi-l cal 4results by any of the methods hitherto 170 known. This is rendered possible by produt-ing a liquid residue and hy attaining a. high yield of zinc at a comparatively slight cost.

In the present process the materials are fed to the furnace in pieces of yany desired size as regards the lower limit, either in a cold or in a heated condition. Nevertheless with previous heating the temperature is not carried so high that the, zinciferous ma- V terials enter the furnace in the form of liquid slag.

I`he process consists in melting the zinciferous materials in a blast furnace on a layer of such materials as cause or facilitate the liberation of zinc., for example, carbon, lime, iron. the melting being effected by heating gases which traverse the zinciferous materials and the materials in the lower layer in a downward direction. In what follows this lower layer is designated the dezincing layer and the materiails composing the same are referred to as dzincing ma tcrials. The de-zinoing layer may rest on a grate which consists preferably of water 95 cooled iipes or the like.

The ollowing among others are know'n as materials which cause or facilitate the liberation of zinc-carbon. linie, lime compounds, iron` and compounds of iron and ox gen. Several ot such materials may he emp oyed simultaneously, the composition of the deziucing layer being so adapted to that of the '/,inciterous materials that a slag as poor as possible in zinc flows away. Indirectly additions of silica alumina, iiuorspar and Cil ess may other materials also facilitate the liberation of zine according to en'eun'istanees. by eausY ing an easily fusible slag.

The 'fragmentary materiale are melted hy the hot gases traversing them and then drip througli the dezinring layer. lleriI they have the oppfirtunity of giving otf zinehy reduction or reaction in passing. however is maintained as tar ae possible in so oxidizing a condition that the zine vapour is converted to zine oxide immediately it is produeed. By these means the heat neces sary for the actual reduetion beeomee praetieally nil` for the heat'used for rednetion is immediately again restored at the same plat-e hy oxidation. A further reault of the oxidizing eharaeter of the t'lame is the prevention oit the separation of iron whieh would otherwise oreur in the ease of moat materials treated. V

The. process ma)v1 he carried on uninterruptedly hy supplyinu. in suitable propor tion with the zineiferomy material. these niaterials, whieh are removed from the dezineing layer h v the molten suhstanee Howing through it. lt is true that in that rase there oeeurs. even above the de-zineing layer. a melting and a rem-tion emmer-ted therewith between the zineit'erom materials; and the materials which afterwards eollert in the demineing layer. xine and zine-oxide being evolved. rl`he latter oeeurrem'e is the saine as 'as desrribed in the patent speeilieation aeeompanying my application for latent Serial No.. TlHRt' tiled on the 3rd Mareh. 1913.

The present. proeess ia to he regarded as an improvement on that last mentioned for the reason that hy' its means even that zine is reeovered whieh'enters the de-zineing layer and io there liherated` for in the other proeess the grate plays approximately the Same part as the upper surfare of the deaineing layer in this. (lwing to the fart that inthe present [i1-west;A the eharge may he deposited in a ronumrativelv thin layer without thereby' rausing a residueY rieh in zine. a llame of a more strongly oxidizing eharaeter mae he maintained whereby.V in addition 'to' the advantages mentioned.. the fuel eonsumption is redini-ed.

The tornare werving to carry on the proe adesignated a blast furnare. Preferably those methods of ronstrnetion are employed whieh were deserihed in the patent Speritiration No. TlHHt of 3rd Mareh. IN1-'fl hereinla-fore referred to. The method ol' working is only altered in aeeorilanei-y with the present prot-ess in that a le-zineing layer ot" .antieient thieknesa is maintined on the grate. lf for examrie, zine in to he rev eovered from slag tiom,ead furnaees. this may mostly he attained in lmfieient degree hy using eolie and lime alone aa materials for the demineing layer.

The llame rl`he heating and melting ot the tra: mentary materiala re-ting on the ilu/ inring layer may he ellerted. l'or e\a|nple. lthe hot gosen ol' a lateral liriI whirh play on to the top ol the rhal'ge. or hy the ront hustion ot' prodneer gm in the pare above the charge or in it. or hv pnlverulent or liquid luel prel'erahly inlrodnrwI I'rom alamhnnnltaneonaly with air. or lo lragmenlary fuel-supplied together \\ith lhe zinril'eroin materials,

The employnn-nt of pnlvernient l`;|el han the special advantage that roal or lu'eeze ol little value ran he uned and that at the same time pierea of eoke Supplied l'or redurtlion ran he saved without materially intiuenring the yield. Then as regarde4 the reduring artion. tln` leas linely ground partit-les4 ol' the pnlverulent fuel l'ullil the eame lash as the fragmentary eolie. for these eoar-er partit-les are earried along hv the stream of gaa and Settle in the liquid slag. ln thi.` manner it is possihle for example to treat -lag l'rom lead fnruaeea h v the present prore x`` with lime only as the le-zineing layer.

.\loreover it is also poseihle to ldow ill air. alone or in eomhination willi r uilahle fuel. laterally from tlnei'reumterenre of the blast fnrnaee into the ieharge through tuyeres. ll'ith fuel supplied in pieve4 the proress may also in this rage he worked in sueh a way that a small portion ot' the gase are allowed to go upwards hut the reet downwardsA 'l`hen the fuel hurna` in front oi" the tuyereaA and the gases in the down wardly travellingr portion meet with approximately the same ronditione' as when air or gases are introdnred exelufively from the upper sui-fare. (hi the other hand the upwardly travelling portion give` np ita heat under more favorable eonditione; on aeeodnl of the opposed dileetiou of llow. manner the eharge Ieaehes the melting zone with a high temperatureand needa` less heat and fuel there than with the exelusive use of the parallel direi-tion of flow. wlnfrehy again the eliararter of the gaanl heroinemore strongly oxidizing. For other purposes and other proresaes the eomluwtion oll fragmentary' fuel in smelling tornai-w hv means of air admitted laterally and travelling downwards only ia in itsellI known.

The hot gaees laden with xine oxide para ing out ofA the dezineing layer may with adV vantage he employed fl I' pre-heating the rau' materials, heating air. or for other purposes. before being treed from zineoxide he one ol' the known methods. `\`o|netime.-: il may' he ireferahle to add air to the gases a t'ler they leave the, furnace. for theeomhnSlion of any earhon monoxide that may he present.

The de-ziming layer may he arranged on `a blaat tornare Hoor imma-rions to-gas. in- Istead otA on a grate. he itl a level` nrlined. or basket grate, and the gases as woll as the ln thi.\'

slag may be led out of the de-zincing layer by means of lateral openings.

lf it is not desired to recover zinc oxide as such but as zinc compound, this can under certain circumstances be effected without previous separation of the zinc oxide from the stream of gas, for example by introducing the gases into aci-d water for the production of sul )hate of zinc (zinc vitriol).

F ine gralned materials such as fine ores, slimes, residue of zinc retorts, and the like, are preferably first briquetted, when the materials added may at the same time be intimately mixed and united with them.

It has already been proposed to effect the liberation of zinc from sla introduced 'into the furnace in a liquid con 'tion by passing it through coke kept continuously red hot by blowing. Here on the contrary it is a case of materials introduced in pieces, and in addition the heating of the de-zincing layer is effected in a fundamentally different manner. lf, for example, coke alone is employed in the present process as the material for the liberation of zinc, and if this is also used for melting by means of air blown in from above, then the combustion to carbon dioxide is effected in the charge of fragmentary material at its upper surface first whereby most of the colte is burned. At this point is produced the highest temperature, which diminishes further downwards when the reduction to carbon monoxide sets in, a corresponding quantity of heat becoming latent. Consequently in the de-zincing layer lying still deeper, no heat is evolved but the tcmperature is only kept up.` Further, owin to the good state of division of the dripping liquid slag, the de-zincing layer only need have a small depth as compared with that for the process mentioned, with slag introduced in a liquid condition. This again causes a small formation of carbon monoxide and hence a saving of fuel. The advantages mentioned are the result of blowing in a downward direction in combination with the de-zincing layer, in which lies a further distinctive characteristic.

Further, it has already been proposed to liberate zinc from ores mixed with bituminous coal upon 'a layer of coal resting on u grate, by means of a ownwardly directed stream of air, and to recover the zinc in the form of zins.` oxide. But in that case the ore was not intended to be melted; so that the residue freed from zinc remained behind on the grate in the form of a sintered mass, that is to say, only imperfectly fused. By this older process therefore, for example, no zinciferous sla from lead furnaces can be treated, but on y ores which melt with difficulty.

As opposed to this, the present process consists not only in the sintering of the zinciferous inaterials but in their complete melting; therefore for example, to ores whichmelt with difficulty and the like, liuxes are added or such materials as allow the ore to take the formv of liquid slag at the temperafrom zinoiferous materials, which consists in arranging zinciferous materials on a layer of de-zincing materials, in melting the zinciferous materials by means of hot combustion gases passing in a downward direction, in passing the molten mass and the gases through said layer, and in withdrawing the molten residue and the gases laden with zinc oxide at the lower side of said layers.

2. Process for the recovery of zinc oxide from slags containing zincespecially lead and copper furnace slags-which consists in arrangin the zinciferous materials on a layer of e-zincing materials, in melting the zinciferous materials by means of hot combustion gases passing in a downward direction, in passing the molten mass and the gases throu h said layer and in withdrawing the mo ten residue and the ases laden with zinc oxide at the lower si e of Said layers, the de-zincing la er being renewed by supplying in sultab e proportion with the zinclferous material those substances removed from the said layer by the molten mass owing through.

3. Process for the recovery of zinc oxide from zinciferous materials which consists in arranging zinciferous materials on a layer of de-zincing materials, in melting the zincifcrous materials by -means of hot combustion gases passing in a downward direction, such combustion gases bein produced internally within the charge and only a part of the gases produced being passed downwards, the rest paing upwards, thereby preheating the charge on its way to the smelting zone.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

Eem-:sr H. L. MUMMENHOFF, IDA Cinner HAFERMANN. 

